BUG/MEDIUM: unique_id: HTTP request counter is not stable

Patrick Hemmer reported that using unique_id_format and logs did not
report the same unique ID counter since commit 9f09521 ("BUG/MEDIUM:
unique_id: HTTP request counter must be unique!"). This is because
the increment was done while producing the log message, so it was
performed twice.

A better solution consists in fetching a new value once per request
and saving it in the request or session context for all of this
request's life.

It happens that sessions already have a unique ID field which is used
for debugging and reporting errors, and which differs from the one
sent in logs and unique_id header.

So let's change this to reuse this field to have coherent IDs everywhere.
As of now, a session gets a new unique ID once it is instanciated. This
means that TCP sessions will also benefit from a unique ID that can be
logged. And this ID is renewed for each extra HTTP request received on
an existing session. Thus, all TCP sessions and HTTP requests will have
distinct IDs that will be stable along all their life, and coherent
between all places where they're used (logs, unique_id header,
"show sess", "show errors").

This feature is 1.5-specific, no backport to 1.4 is needed.

doc/configuration.txt

@@ -11438,7 +11438,7 @@ Please refer to the table below for currently defined variables :
   |   | %pid | PID                                           | numeric     |
   | H | %r   | http_request                                  | string      |
   |   | %rc  | retries                                       | numeric     |
-  | H | %rt  | http_request_counter                          | numeric     |
+  |   | %rt  | request_counter (HTTP req or TCP session)     | numeric     |
   |   | %s   | server_name                                   | string      |
   |   | %sc  | srv_conn     (server concurrent connections)  | numeric     |
   |   | %si  | server_IP                   (target address)  | IP          |

include/types/global.h

@@ -90,7 +90,7 @@ struct global {
 	int rlimit_memmax;	/* default ulimit-d in megs value : 0=unset */
 	long maxzlibmem;        /* max RAM for zlib in bytes */
 	int mode;
-	unsigned int req_count; /* HTTP request counter for logs and unique_id */
+	unsigned int req_count; /* request counter (HTTP or TCP session) for logs and unique_id */
 	int last_checks;
 	int spread_checks;
 	char *chroot;

src/log.c

@@ -111,7 +111,7 @@ static const struct logformat_type logformat_keywords[] = {
 	{ "pid", LOG_FMT_PID, PR_MODE_TCP, LW_INIT, NULL }, /* log pid */
 	{ "r", LOG_FMT_REQ, PR_MODE_HTTP, LW_REQ, NULL },  /* request */
 	{ "rc", LOG_FMT_RETRIES, PR_MODE_TCP, LW_BYTES, NULL },  /* retries */
-	{ "rt", LOG_FMT_COUNTER, PR_MODE_HTTP, LW_REQ, NULL }, /* HTTP request counter */
+	{ "rt", LOG_FMT_COUNTER, PR_MODE_TCP, LW_REQ, NULL }, /* request counter (HTTP or TCP session) */
 	{ "s", LOG_FMT_SERVER, PR_MODE_TCP, LW_SVID, NULL },    /* server */
 	{ "sc", LOG_FMT_SRVCONN, PR_MODE_TCP, LW_BYTES, NULL },  /* srv_conn */
 	{ "si", LOG_FMT_SERVERIP, PR_MODE_TCP, LW_SVIP, NULL }, /* server destination ip */
@@ -1512,13 +1512,13 @@ int build_logline(struct session *s, char *dst, size_t maxsize, struct list *lis
 
 			case LOG_FMT_COUNTER: // %rt
 				if (tmp->options & LOG_OPT_HEXA) {
-					iret = snprintf(tmplog, dst + maxsize - tmplog, "%04X", global.req_count++);
+					iret = snprintf(tmplog, dst + maxsize - tmplog, "%04X", s->uniq_id);
 					if (iret < 0 || iret > dst + maxsize - tmplog)
 						goto out;
 					last_isspace = 0;
 					tmplog += iret;
 				} else {
-					ret = ltoa_o(global.req_count++, tmplog, dst + maxsize - tmplog);
+					ret = ltoa_o(s->uniq_id, tmplog, dst + maxsize - tmplog);
 					if (ret == NULL)
 						goto out;
 					tmplog = ret;

src/proto_http.c

@@ -8202,6 +8202,7 @@ void http_reset_txn(struct session *s)
 	s->target = NULL;
 	/* re-init store persistence */
 	s->store_count = 0;
+	s->uniq_id = global.req_count++;
 
 	s->pend_pos = NULL;
 

src/session.c

@@ -119,7 +119,7 @@ int session_accept(struct listener *l, int cfd, struct sockaddr_storage *addr)
 
 	s->logs.accept_date = date; /* user-visible date for logging */
 	s->logs.tv_accept = now;  /* corrected date for internal use */
-	s->uniq_id = totalconn;
+	s->uniq_id = global.req_count++;
 	p->feconn++;
 	/* This session was accepted, count it now */
 	if (p->feconn > p->fe_counters.conn_max)